Background: Adipose stem cells represent a heterogenous population. Understanding the functional characteristics of subpopulations will be useful in developing adipose stem cell-based therapies for regenerative medicine applications. The aim of this study was to define distinct populations within the stromal vascular fraction based on surface marker expression, and to evaluate the ability of each cell type to differentiate to mature adipocytes. Methods: Subcutaneous whole adipose tissue was obtained by abdominoplasty from human patients. The stromal vascular fraction was separated and four cell populations were isolated by flow cytometry and studied. Candidate perivascular cells (pericytes) were defined as CD146/CD31/CD34. Two CD31 endothelial populations were detected and differentiated by CD34 expression. These were tentatively designated as mature endothelial (CD 31/CD34), and immature endothelial (CD31/CD34). Both endothelial populations were heterogeneous with respect to CD146. The CD31/CD34 fraction (preadipocyte candidate) was also CD90 but lacked CD146 expression. Results: Proliferation was greatest in the CD31/CD34 group and slowest in the CD146 group. Expression of adipogenic genes, peroxisome proliferator-activated receptor-γ, and fatty acid binding protein 4, were significantly higher in the CD31/CD34 group compared with all other populations after in vitro adipogenic differentiation. This group also demonstrated the highest proportion of AdipoRed lipid staining. Conclusions: The authors have isolated four distinct stromal populations from human adult adipose tissue and characterized their adipogenic potential. Of these four populations, the CD31/CD34 group is the most prevalent and has the greatest potential for adipogenic differentiation. This cell type appears to hold the most promise for adipose tissue engineering.
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